Ok, sorry, I have to step in here and defend William Shatners honour here. He's a great actor, Boston Legal proves he can act now ("DENNY CRANE!") and Judgement At Nuremburg (1961), where he acts opposite the likes of Burt Lancaster and some of the finest film actors to have ever graced the silver screen and holds his own (In some scenes, despite playing a relatively minor character he acts these much bigger names off the screen) proves he was a great actor then as well.
In Star Trek (1966-1969) he just didn't take it seriously- his 'unique way of acting' as some put it, and the so called "Shatner-speak" is in fact a thing called Iambic Pentameter- which is how Shakespeare wrote. He was simply drawing on his experience of doing Shakespeare in an inappropriate setting, and gets panned for it. He was unlucky that he became known for a part he hammed up to ridiculousness, and then the obsession kicked in (Which included having his commode be a replica of the Enterprise Captains Chair) but once he got past Star Trek and learned to laugh at himself, fantastic things like the aforementioned Denny Crane happened.
As for Liam Neeson being in Star Wars- he was only in the Phantom Menace, which doesn't count.